The Hidden Power Beneath Our Feet
Geothermal energy, quite literally the “heat from the Earth,” is a renewable resource that is far more accessible and abundant than many realize. While the dramatic geysers and hot springs of Iceland capture the public imagination, the true potential of geothermal power often remains hidden from view, waiting to be tapped across the globe.
Geothermal energy has the remarkable ability to provide electricity, heating, cooling, and even energy storage – all from the natural heat radiating from deep within our planet. As the world transitions towards a clean energy future, this versatile resource is poised to play a pivotal role in powering our schools, homes, and communities in a sustainable way.
“The Earth itself is a renewable energy source,” explains Amanda Kolker, Geothermal Laboratory Program Manager at the National Renewable Energy Laboratory (NREL). “Earth’s heat is always available; it doesn’t go away when the sun goes down. It can play a big role in the energy transition by providing reliable, 24/7 clean energy, and it can do so much more than people think.”
In this in-depth article, we’ll uncover the hidden potential of geothermal energy, exploring how researchers and innovators are harnessing this powerful resource to meet our evolving energy needs – from generating electricity to providing heating and cooling, storing energy, and even extracting critical minerals. Get ready to discover the remarkable ways the Earth can help save the planet.
Peering Below the Surface: Identifying Hidden Geothermal Treasures
Geothermal resources are present on every continent, but many of the most promising systems are “hidden” deep underground, with no visible signs on the surface. This poses a unique challenge for scientists and developers looking to tap into these valuable resources for electricity generation.
“If the resource is hidden, how do you know where to drill?” This was the question that a research team from Sandia National Laboratories set out to answer, with funding from the U.S. Department of Energy’s Geothermal Technologies Office.
Working in Nevada’s Steptoe Valley, the team focused on a specific type of hidden geothermal system known as a “stratigraphic hydrothermal resource.” These systems are characterized by sedimentary rocks, geothermal heat, and high porosity and permeability – features that could allow a single exploration effort to support multiple geothermal power plants, making the process more efficient and cost-effective.
To better understand the subsurface structure and potential power capacity of the Steptoe Valley resource, the researchers primarily relied on geophysical imaging techniques. These non-invasive methods produce 2D or 3D models of the underground environment, offering a way to explore the geology without the high costs and environmental impact of traditional drilling.
“Geophysical imaging provided subsurface characterization sufficient for conceptual modeling and initial reservoir analyses,” the researchers reported. Moreover, they found that this approach was most effective when combined with geological and geochemical data from surface and borehole studies.
By enhancing our understanding of hidden geothermal systems and showcasing the effectiveness of geophysical imaging, this project is helping to enable better and more cost-effective exploration and characterization of geothermal resources worldwide. The researchers have published their findings openly, expanding opportunities for other researchers, developers, and the public to leverage these insights.
“GTO’s website offers more information about research and opportunities in hydrothermal resources,” the article notes, inviting readers to further explore the U.S. Department of Energy’s Geothermal Technologies Office and its ongoing efforts to unlock the hidden potential of geothermal energy.
Harnessing the Earth’s Heat: Geothermal’s Diverse Applications
Geothermal energy is a true powerhouse, offering a wide range of applications that can contribute to the clean energy transition in remarkable ways. Far beyond just generating electricity, geothermal can provide heating and cooling, enable energy storage, and even help extract critical minerals essential for the next generation of clean technologies.
“Geothermal is a triple resource: an energy source for heating, cooling, and power; a storage resource; and a mineral resource,” Kolker explains. “The Earth itself has the potential to address a variety of hurdles in the transition to a clean energy future.”
Electricity, Heating, and Cooling
Geothermal power plants have been delivering renewable electricity for more than a century, tapping into the heat radiating from the Earth’s interior. These plants can operate using temperatures ranging from just 250°F to 700°F, making them a viable option in many regions.
But the benefits of geothermal energy don’t stop there. The consistent 50°F to 60°F temperatures found just 10 feet underground can be harnessed for direct heating and cooling applications, using modern heat pump technologies. This means that geothermal can provide renewable heating in the winter and cooling in the summer for individual buildings, campuses, and even entire communities.
“It doesn’t have to be this amazing, dramatic volcano,” says Whitney Trainor-Guitton, a geoscience researcher at NREL. “We can use 55°F groundwater to heat and cool bus terminals, college campuses, and even whole towns.”
While most geothermal heat pump installations in the U.S. have been for individual buildings, these technologies are used worldwide for heating and cooling large networks of interconnected buildings, known as district heating and cooling systems. These systems can integrate geothermal with other renewable energy sources and thermal energy storage, providing added flexibility and resilience for communities.
Energy Storage and Grid Integration
Geothermal energy also has the potential to serve as a long-duration energy storage solution, helping to address the intermittency of renewable sources like solar and wind. By storing excess energy as thermal energy underground, the Earth itself can act as a massive “battery,” releasing the stored heat when needed to generate electricity or provide heating and cooling.
“Imagine if, instead of using a battery, the Earth itself could store energy—and not just enough for your house: enough to provide energy to multifamily buildings, colleges, neighborhoods, and even entire cities,” the article suggests.
NREL researchers are exploring the commercial viability of gravity-based mechanical storage systems that can use depleted oil and gas wells to store electrical energy as potential energy by lifting a multi-ton weight within a wellbore. This technology could also be used inside inactive geothermal wells for long-term storage.
By pairing geothermal with other renewable technologies, such as concentrating solar power, communities can create hybrid systems that take advantage of the strengths of both, maximizing power plant performance and storage capabilities.
“By pairing solar and geothermal, we can design a system that naturally incorporates and takes advantage of the superior aspects of both technologies,” says Guangdong Zhu, NREL’s group manager of thermal energy systems. “The solar can increase the heat for the geothermal system, leading to more electricity generation, and the geothermal system can store excess energy from the solar.”
Mineral Extraction and the Clean Energy Transition
Geothermal energy also has the potential to contribute to the supply of critical minerals, such as lithium, which are essential for the production of rechargeable batteries used in electric vehicles, pacemakers, and countless other clean energy technologies.
“As we transition to electric vehicles and battery storage for solar and wind power, the need for lithium is rising,” Kolker notes. “Geothermal energy may be able to help in a sustainable way.”
Recent studies have shown that it is economically feasible for geothermal brines to yield approximately 24,000 metric tons of lithium per year – enough to establish a secure, domestic supply of this scarce mineral. One area with particularly high potential is California’s Salton Sea region, which has significant geothermal resources and opportunities for direct lithium extraction.
By leveraging geothermal resources to extract critical minerals, the clean energy transition can become more self-reliant, reducing the need for energy-intensive and environmentally-taxing mining operations. This not only benefits the planet but also has the potential to create new jobs and economic opportunities in communities across the country.
Expanding Geothermal’s Reach: Emerging Technologies and Innovative Approaches
While geothermal power plants have been providing clean energy for over a century, new technologies and innovative approaches are opening up the potential for geothermal energy to be tapped in previously inaccessible regions.
Enhanced Geothermal Systems (EGS)
One such technology is enhanced geothermal systems (EGS), which can bring the missing components (water or pathways through the rock) to areas where the natural conditions are not ideal for traditional geothermal power generation.
“The U.S. Department of Energy is putting a great deal of investment into EGS with the recent Enhanced Geothermal Shot as part of the Energy Earthshot initiatives, funding for new EGS demonstration sites, and the current Utah FORGE demonstration site,” explains Koenraad Beckers, a thermal sciences researcher at NREL.
Through collaboration between national laboratories, universities, and industry partners, projects like the EGS Collab are helping to bridge the gap between laboratory tests and full-scale EGS deployment, paving the way for wider adoption of this promising technology.
Closed-Loop Geothermal Systems
Another emerging approach is closed-loop geothermal, also known as advanced geothermal systems. These systems use engineered pipe systems to circulate water or another heat transfer fluid through the hot rock, rather than relying on natural underground pathways.
“With closed-loop systems, you keep the fluid within your well and pipes, and the pipes are exposed to the hot rock,” Beckers explains. “NREL can simulate both EGS and closed-loop systems for industry and government partners, providing important pre-validation that is required before major investments are made deploying new technologies.”
Supercritical Geothermal Resources
Looking even further into the future, researchers are exploring the potential of supercritical or superhot geothermal resources, which exceed the critical point of water (where liquid water and vapor are indistinguishable). Tapping into these extra-hot systems could potentially produce 5-10 times the power of a commercial geothermal well today.
“The energy from a single superhot geothermal well could produce 5–10 times what a commercial geothermal well produces today,” Kolker says. “If we can find and produce these systems, this could be a game-changer.”
Through the DEEPEN project, a multinational collaboration, NREL is working to develop new methods for exploring and characterizing these transformative geothermal resources.
Revitalizing Existing Infrastructure: Repurposing Oil and Gas Wells
While emerging technologies are crucial for expanding geothermal’s reach, there are also opportunities to leverage existing infrastructure to accelerate the deployment of geothermal energy.
Thousands of oil and gas wells have already been drilled across the country, and some of these can be repurposed for geothermal energy generation or coproduction with ongoing hydrocarbon extraction.
“Exploratory drilling is a huge upfront cost for geothermal development,” Kolker explains. “But there are thousands of oil and gas wells across the country that have already been drilled, some of which can be either repurposed for geothermal or used for coproduction of geothermal and hydrocarbons.”
Two projects are currently underway in Oklahoma and Nevada, aiming to generate 1 MW or more of power from repurposed oil and gas wells. One project seeks to create a roadmap for “geothermal cogeneration,” while the other aims to bring an abandoned well back to life for geothermal energy production.
Moreover, when wells cannot be repurposed, the investment in drilling new wells can be used to push the boundaries and create novel drilling techniques. The Geothermal Limitless Approach to Drilling Efficiencies (GLADE) project, for example, is working to drill twin high-temperature (572°F) geothermal wells deeper (up to 20,000 feet) and more quickly than most existing wells, with the goal of reducing project timelines and costs for developing geothermal power plants.
By leveraging existing infrastructure and developing innovative drilling techniques, the geothermal industry can accelerate the deployment of this renewable resource, helping to power more schools, homes, and communities across the country.
Bringing Geothermal to Your Community
While some regions, like the western United States, are naturally endowed with high-temperature geothermal resources suitable for large-scale power generation, the benefits of geothermal energy can be harnessed in communities across the country.
“Anywhere in the country, if you drill, it gets hotter and hotter with each mile you go deeper,” Beckers explains. “In the western United States, that temperature increases fast: If you drill just 1–2 miles deep, you have temperatures hot enough for electricity. To get those temperatures in eastern states, you might need to drill miles and miles down, but you can use lower temperatures to directly heat or cool campuses, neighborhoods, and even towns.”
For community-scale heating and cooling systems, geothermal boreholes are usually drilled 10–500 feet deep, providing a constant temperature that can be used to both heat and cool buildings via heat pumps. These district systems use a network of pipes to circulate water between the buildings, with an energy station managing the heating and cooling as needed.
“At just 10 feet below the surface, the temperature remains the same year-round—around 55°F,” Kolker says. “This means in the summer geothermal technology can provide cooling, and in the winter it can provide heat.”
Such community-scale geothermal systems can be integrated with other renewable energy sources and thermal energy storage to create resilient, decarbonized microgrids. NREL is helping communities analyze these geothermal microgrid technologies, providing valuable insights and support as they explore ways to harness the Earth’s heat for their energy needs.
Conclusion: Geothermal’s Pivotal Role in the Clean Energy Transition
As the world transitions towards a more sustainable energy future, geothermal energy is poised to play a pivotal role in powering our schools, homes, and communities. Whether it’s generating electricity, providing heating and cooling, enabling energy storage, or extracting critical minerals, the Earth’s natural heat is a renewable resource with remarkable versatility.
“At any scale, a decarbonized grid is going to be a mixture of renewable technologies, including geothermal,” Kolker affirms. “That is the future.”
Through the innovative work of researchers, scientists, and industry partners, the hidden potential of geothermal energy is being unlocked, making it accessible to more people and communities around the world. By tapping into this renewable resource, we can take a significant step towards a cleaner, more sustainable tomorrow.
To learn more about the latest developments in geothermal energy and how you can get involved, be sure to visit the National Renewable Energy Laboratory’s website and the U.S. Department of Energy’s Geothermal Technologies Office. Together, we can harness the power of the Earth and power a brighter future for all.
